Evaluation of Ni–Al coatings processed by plasma transferred arc

Abstract

Higher efficiency processes are strongly dependent on the ability to process materials/components that can sustain more aggressive service conditions. β-NiAl intermetallic alloys are known for exhibiting superior high temperature properties, but are difficult to process. This study evaluated Ni–Al coatings processed in situ by plasma transferred arc (PTA) welding. Coatings processed with mixtures of Ni and Al powders, Al content within the range 15–50 wt-%, were analysed. In situ development of Ni aluminides was confirmed by X-ray diffraction analysis. Increasing aluminium (Al) content in the deposited mixture increased the penetration depth. The microstructure of coatings depended on the amount of Al in the deposited powder mixture associated with the exothermal synthesis of the β-NiAl intermetallic compound. The present study presents an important step towards the protection of components for equipment of higher efficiency processes, as results validated the potential of PTA hardfacing as a processing technique for surface tailoring.

Keywords:

• Plasma transferred arc
• Hardfacing
• Nickel aluminides
• Microstructure

The authors would like to thank CNPq – Conselho Nacional de Pesquisa for the scholarship given to Ms V. A. B. Almeida and for funding the research activities.